The present invention relates in general to control of contamination within the environment of electrostatographic reproduction apparatus, and more particularly to a contamination control device for the development station of the reproduction apparatus.
In typical commercial reproduction apparatus (for example, electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles, contained in a development station, are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member, and an electric field is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric member, and the transferred image is fixed to the receiver member by heat and/or pressure to form a permanent reproduction thereon.
One type of development station commonly used in electrostatographic reproduction apparatus is referred to as a magnetic brush development station. An exemplary magnetic brush development station, such as shown in US Pat. No. 4,878,089 (issued Oct. 31, 1989, in the name of Gustlits et al), includes a housing providing a reservoir for a supply of developer material. The developer material may be, for example, a two component material comprising magnetic carrier particles and relatively smaller pigmented marking particles. A mechanism such as a paddle wheel, auger, or ribbon blender, is located in the reservoir and serves to stir the carrier particles and the marking particles to triboelectrically charge the particles so that the marking particles adhere to the surfaces of the carrier particles. A transport mechanism brings the developer material mixture into the field of a plurality of magnets which, in turn, apply the marking particles to the latent image charge pattern on the dielectric member to adhere to the pattern forming the developed image.
It is well known that while the magnetic brush development station has been perfected to the point where, in general, it is quite efficient in developing latent image charge patterns, it still tends to generate considerable airborne particulate matter. This is due to the high turbulence during mixing and, at least in part, to the fact that during mixing certain particles remain uncharged, receive only a low charge, or acquire a wrong sign charge. These particles readily become airborne rather than flowing with the remaining developer material mixture via the transport mechanism into the magnetic development field.
Such airborne particulate matter, if left uncontrolled, may escape from the developer station and cause the interior of the reproduction apparatus to become contaminated. This can adversely effect the reproduction apparatus causing operating problems and/or degraded copy output. Moreover, the contamination may eventually escape to the environment surrounding the reproduction apparatus and unduly contaminate such environment. Accordingly, certain electrostatographic reproduction apparatus have provided contained exhaust systems operatively associated with the respective development stations. While such systems have been shown to reduce airborne particulate contamination associated with magnetic brush development stations, they are not completely efficient, and thus allow adverse contamination to build up in the reproduction apparatus and its environment.